Hammer mills with resilient seal



Jan. 2], 1958 A. B. HANSE HAMMER MILLS WITH RESILIENT SEAL Filed Jn. 4, 1954 INVENTOR. a2 fime Unite tates HAMMER MILLS WITH RESILIENT SEAL Application January 4, 1954, Serial No. 401,860

3 Claims. (Cl. 241-239) In some forms of hammermills, it is desirable to have a yieldable bar positioned near the circular path of the hammers. The yieldability of the bar is especially important where the hammers are rigidly mounted on their rotors. Ordinarily the yieldable bar may never move, but if a piece to tramp iron or other unbreakable material should be dumped into the hammermill with a load of rock or other material being crushed, there might be disastrous breakage of parts unless some part was yieldable.

In some designs, the yieldable bar may be positioned quite close to a screen grating. For example, in the form of hammermill or impact rock crusher manufactored by the assignee of this application, the fragments resulting from the initial impact of the hammers are thrown toward a grating so the pieces not already broken to size are returned to the hammers. A heavy stripper bar is located adjacent the bottom of the grate and extends between it and the circular path of the hammers, being adjustable fora variety of spacings from the path of the hammers. In the long periods when nothing occurs to shift the stripper bar, dust or other small fragments of rock tend to pack themselves between the stripper bar and the adjacent grate; This is objectionable because these particles become packed so tightly that they tend to bind the stripper bar in place. Aside from the possibility that this might interfere with the resilient yielding of the bar when required, it also interferes with the removal of the bar for replacement or repair of worn parts. I I

According to the present invention, this difficulty is entirely overcome by providing a resilient seal, preferably of foam rubber, throughout most of the space where the packing has occurred. In spite of the fact that most of the other parts with which the rock comes in contact have to be formed of manganese steel in order to hold up satisfactorily, it has been found possible to so locate the sealing rubber that it is suificiently protected from the rock by surrounding metal parts so that it has a satisfactorily long life.

Additional objects and advantages will be apparent from the following description and from the drawings.

each new inventive concept therein no matter" how it may later be disguised by variations in form or additions of further improvements; and the appended claims are an tended't'o accomplish this purpose by particularly pointatent ing out the parts, improvements, or combinations in which the inventive concepts are found.

The form of hammermill chosen for illustration of the present invention is approximately that found in a prior co-pending application in which the present inventor was a co-inventor. This application is Serial No. 201,364, filed December 18, 1950, now Patent No. 2,767,928, granted October 23, 1956, and entitled Impact Rock Breakers, the other applicant there being Fred W. Rollins. The disclosure of that application is incorporated herein by reference.

As more fully described there, a plurality of hammer" rotors 11, of which only one has been shown here, each carry a plurality of hammers 12 fixed thereon and extending the length of the rotor. The hammer bars 12 smash the rock which is dropped into their path and fragments are thrown against a deflector screen grating or grate 13. Some pieces which are sutficiently reduced in size pass between the bars of the grating 13 and fall to discharge through the discharge space 14. Oversize pieces are retained in the breaker chamber 16 and fall again into the path of the hammers 12.

For various reasons, a stripper bar 17 is interposed between the grate 13 and the path of the hammers,- called the hammer circle. The exposed portion of the stripper bar is a stripper bar head 18 which is made of manganese steel and is preferably shaped approximately as shown to improve the stripping action of the bar. A relatively small percentage of the rock will be broken against the stripper head 18, more of it being deflected upwardly so that it will again drop down in front of the hammers 12 and be broken by free impact action. No doubt there is an occasional piece of rock which is crushed by a squeezing action between a hammer l2 and the stripper head 18. The positioning of the stripper bar is pref erably adjustable toward and from the hammer circle; The clearance between the stripper bar and the hammer circle determines to some extent the size of rock fragments which will pass between them and this afiects' the size of the ultimate output even though there is a second grate 19 against which much of such rock would be thrown. Another reason for adjustability of the position ing of the stripper bar is to compensate for wear on the stripper head 13.

Occasionally some unbreakable material finds its way into the crusher chamber 16. This might, for example, be the manganese steel tooth of a power shovel or dipper.

it is important that there be yieldability so that if such a piece of tramp iron be caught between a hammer 12 and stripper head 18 the equipment will not be wrecked. As disclosed in the prior application mentioned, the

stripper bar 17 is made yieldable, but is normally held firmly in position.

Construction and mounting of stripper bar In the illustrated form of the invention, stripper head 18 is carried on a casting 21, which comprises two transverse bars 22 and 23 held integrally together by a series of spaced webs 24. The head 18 may be provided with shanks 2.6 into which bolts 27 lit, the' bolts 27 being drawn rearwardly by nuts 28 to draw the head 18 firmly onto the casting 21. The nuts 28 bear against a plate 29 resting on the casting 21.

The casting 21 extends through theside walls of the hammer mills, in each of which a slot 31 has been provided. The edges of this slot are reinforced so as to pro vide a suitable slideway for the casting 21. Ateaclr endof the casting, outside of the side wall, the casting 21 ispivotally secured to a link 33. The two links 33 are on oppositesides of the hammer mill and are eachpivoted to a crank arm 3 3-, the two crank arms being carried by torque tube 36. The torque tube 36 is urged by spring I 7 bars 37 in a direction which will return the crank arms 34 counter-clockwise as viewed in Fig. 1 so as to thrust the stripper bar 17 to the position shown. The links 33 and 34 are stopped just short of dead center position by a stop 38 which may be adjustable. The strength and tension of the spring bars37 is preferably such that the stripper bar 17 ordinarily remains motionless. In other words, when only the intended material is going through the hammer mill, any occasional piece which becomes caught between a hammer 12 and stripper bar head 18 will be crushed instead of forcing the stripper bar rearwardly. However, if a piece of very much greater hardness should be caught in the same, way it would, under the terrific force exerted on it by hammer 12 and in turn exerted by it on stripper head 18 force the stripper bar rearwardly. The linkage 33-34 would swing upwardly, the toggle action being accompanied by a partial rotation of the link or crank arm 34 and torque shaft 36 against the tension of springs 37.

It is desirable for the stripper bar 17 to be quite close to the grate or receiving member 13 so that the upper faceof the main body of stripper bar 17 will be protected from the flying rock fragments. On the other hand, a sliding fit would be undesirable because of necessitating very careful fitting of the parts and this would, be expensive. It would be very inconvenient when parts became damaged or worn and had 'to be changed. In the past, when a clearance has been provided between the parts of the stripper bar and the grate 13, there has been occasional trouble with binding by packed rock dust. In the dusty conditions encountered in rock crushers, dust will of course find its way into all crevices. After some dust had accumulated in the particular clearance in question, there was a tendency for it to become firmly packed, probably due to a combination of vibration and a packing effect resulting from occasional high speed movement of tiny fragments or dust particles into the cavity in a direction such that it would strike the dust already accumulated there and pack it tight. Under some conditions, there is a little clay present which tends to produce firm binding of the particles of rock dust to one another. In any event, the net effect has been that there would occasionally be binding between the grate 13 and the stripper bar so that the stripper bar was much more difiicult to move than should be the case.

- An unfortunate factor of this rare trouble is that in a sense it was most likely to be encountered by the best operators. An operator who left the spring 37 too slack or who frequently permitted foreign bodies to get mixed with his rock might never encounter the difficulty. An operator who succeeded in keeping his rock clean for month after month and who had the proper tension on his spring 37 was quite likely to encounter difiiculty when he tried to move the stripper bar for adjustment or for replacing a worm part. There was always at least. a theoretical possibility that this good operator would not have the yieldability protection for which the apparatus was designed because the stripper bar might conceivably fail to shift, even when the unbreakable object was caught between the stripper head 18 and a hammer 12. Of course in this event themomentum of the hammer 12 and its rotor 11 causes it to keep on rotating, regardless. Something would break.

Flexible seal According to the present invention, this difliculty is overcome by providing'a flexible seal 41 between the stripperbar and the grating 13. This resilient seal should fill up nearly all of the space over the stripper bar 17, between it and grate 13, so that there will be no place'of any substantial extent for rock dust to pack. The front edge 42 of resilient seal 41 may be far enough back of stripper head 18 so that even with the stripper bar advancedto the most forward position likely, the resilient seal 41 will not be exposed. The front face of resilient seal 41 is protected by a confining bar 43 which is welded to the crosspiece 23 and extends from side to side of the hammer mill. It also extends close enough to the bottom of grate 13 so as to merely have a safe operating clearance. Of course when the stripper bar is positioned for a long time in the position shown, some rock dust will gatherin this clearance and may become packed. However, this is a short enough space in the direction of move ment so that this small amount of packing is easily disrupted upon moving the stripper bar. The rear face of resilient seal 41is protected by plate 29, which also extends fairly close to the grating 13. In this instance, however, the protection is hardly necessary and the plate 29 therefore serves mainly as a confining member.

Although there are many resilient materials which could be used, one which has been found to be satisfactory is foam rubber with an outer skin forming the surface at the top thereof which engages and slides on the other surface of grate 13. It has been the practice, even before providing the resilient seal 41 to provide grates 13 with a rearwardly extending flange 44. According to the present invention, this is extended further. This may be done by welding a bar 46 to the rear end of flange 44. Of course the bottom surface, formed jointly by grate l3, flange 44 and bar 46, should be a continuous and fairly smooth surface. The ordinary texture of casting, with burrs removed, is sufficiently smooth, however, the thickness of the resilient seal member 41 being fairly substantial so that it easily accommodates itself to smooth irregul'arities.

' From the foregoing, it is seen that the difliculty of binding between the movable bar, such as the stripper bar 17, and a fixed member, such as the receiving memberor grate 13, has been dependably overcome. Although the invention has been illustrated in connection with a stripper bar and a grate, where perhaps it has its greatest utility, it might be useful in other instances wherever a breaker bar or other receiving member in a hammer mill is movable along a surface but may remain immobile with respect thereto so long that binding due to packing of the dust of the rock or other material crushed might result.

I claim:

1. A hammer mill including a hammer rotor having hammers thereon for smashing material dropped into the path of the hammers, a stationary receiving member for intercepting theflight of fragments from the hammer, a bar located between the receiving member and the hammer circle, means for yieldably mounting the bar to maintain it in position during normal operation of the hammer mill but permitting it to shift away from the hammer circle if an unbreakable object should be caught between the bar and a rotating hammer, and a seal of soft resilient material compressed between the receiving member and the bar carried by one of them and sliding on the other, to prevent the binding of the bar by the packing of minute fragments of crushed material between the receiving member and the bar; and member .by'which the resilient seal is carried including confining means extending approximately to the other member for confining the resilient seal and for shielding it from the crushed material, said confining means being spaced with clearance from the other member to avoid sliding engagement therewith.

2. A hammer mill according to claim 1 in which the resilient material is foam rubber.

3. A hammer mill including a hammer rotor having hammers thereon for smashing material dropped into the path of the hammers, a stationary receiving member for intercepting the flight of fragments from the hammer, a bar located between the receiving member and the hammer circle, means for yieldably mounting the bar to maintain it in position during normal operation of the hammer mill but permitting it to shift away from the hammer circle an unbreakable object should be caught between the bar and a rotating hammer, and a foam rubber seal compressed between the receiving member and the bar carried by one of them and sliding on the other, to prevent the binding of the bar by the packing of minute fragments of crushed material between the receiving member and the bar, said foam rubber seal having an outer skin in engagement with the member with respect to which it slides.

References Cited in the file of this patent UNITED STATES PATENTS Re. 20,440 Westberg et a1. July 6, 1937 6 Palmer Apr. 10, 1866 Straker Mar. 14, 1893 Buchanan Nov. 12, 1912 Sherwood Oct. 31, 1922 Povey Apr. 8, 1924 Borton May 14, 1929 Heisserman 1- Oct. 12, 1937 Abbe July 5, 1938 Gruender Oct. 10, 1944 Symons Mar. 14, 1950 FOREIGN PATENTS Australia Aug. 20, 1936 

